Does the minimum
A former high performer now arrives at nine, leaves at five, and says nothing in meetings.
Rule out first
Health, caring duties, a second job. A deliberate and fair rebalancing they're entitled to. Being underpaid for the work.
What could explain it
Role conflict and ambiguity: They don't know what's expected or have conflicting bosses; clear priorities bring effort back within weeks.
Organisational justice: Effort dropped after a specific unfair event: a promotion, a pay decision, being overruled publicly.
Burnout: Exhaustion, cynicism and a sense that nothing they do matters, after a long stretch of overwork; outside work they're tired but intact.
Major depression: The flatness is everywhere, not just at work, with changes in sleep and appetite and loss of interest in things they used to enjoy.
Social loafing: Effort drops only in group work where their share can't be seen; give them visible individual ownership and it returns.
A next move
Ask what changed and when. A specific event points to justice; exhaustion and cynicism to burnout; confusion to role ambiguity. Ask about life outside work too, gently.
If it’s you
When did I stop caring, and what happened just before?